clinical microbiology review - asclsga.org
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Tera Webb, MS, MLS(ASCP)CM
Clinical and Diagnostic Sciences
teralw@uab.edu
Clinical Microbiology Review
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• Beta- Lactams
• Glycopeptides
• Polymyxins
• Quinolones
• Rifamycin
• Aminoglycosides
• Tetracylines
• Macrolides or MLS
• Sulfa
• Trimethoprim
• Nitrofuratonine
Antibiotic Targets
TARGET
Cell Wall
DNA and RNA
Synthesis
Metabolic Pathways
Protein Synthesis
Cell Membrane
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• Blood agar plates (BAP)
• Chocolate agar (CHOC)
• Thayer-Martin agar (TM)
• HBT (Human Blood Tween Bilayer)
• CIN (cefsulodin-irgasan-novobiocin)
• NYC (New York City)
• HE (hektoen enteric)
• XLD (xylose lysine deoxycholate)
• TCBS (Thiosulfate-citrate-bile sucrose)
• SS (Salmonella-Shigella)
• Regan Lowe
• Bordet-Gengou
Culture Plates
• CVA (cefoperazone, vancomycin, amphotericin B)
• CCFA (cycloserine cefoxitin fructose agar)
• SMAC (Sorbitol MacConkey)
• BBE (Bacteriodes Bile Esculin)
• EYA (Egg Yolk Agar)
• LKV (Kanamycin-Vancomycin-Laked Blood)
• Tomato Juice Agar
• Mueller Hinton
• McCoy
• Middlebrook 7H11
• CIN
• Cystine glucose blood agar
3
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• Most common pathogen
• Media
• Microscopic
Staphylococcus
• Staphylococcus aureus
• Staphylococcus epidermidis
• Staphylococcus saprophyticus
• Staphylococcus lugdunersis
4
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• Gram Stain• GPC in clusters
• Colony Morphology• Round, smooth, creamy, yellow to white colonies with beta- hemolysis
• Biochemical tests• Catalase• Coagulase
• Pathology
• Virulence Factors• Enterotoxins• Cytolytic toxins• Extracellular Enzymes• Protein A
Staphylococcus aureus
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• Gram Stain
• GPC in clusters
• Colony Morphology
• Round, smooth, creamy, yellow to white colonies with no hemolysis
• Biochemical Tests
• Catalase
• Coagulase
• Pathology
Staphylococcus epidermidis
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• Staphylococcus saprophyticus
• Add’l Biochemical: Novobiocin
• Pathology:
• Staphylococcus lugdunensis
• Add’l Biochemical: PYR
• Pathology:
Other Coag-Negative Staphylococci
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• Abnormal susceptibility patterns
• Beta-lactam resistance
• MRSA• Screening vs Diagnostic
• Treatment with vancomycin
• VISA and VRSA• Limitations to disk diffusion & automated methods
• Macrolide resistance• Resistance to clindamycin may not be obvious
• D test - Use erythromycin and clindamycin disks
• Inducible resistance is growth between disks but not on side of clindamycin disk
Staphylococcus - Antimicrobial Susceptibility 8
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Streptococci and Enterococci are speciated based on hemolysin production and biochemical properties.
• α-Hemolysis
• RBCs are partially lysed, resulting in a greening of the area around the colony
• β-Hemolysis
• RBCs are completely lysed, resulting in a clear area around the colony
• γ-Hemolysis (nonhemolytic)
• RBCs are not lysed, so there is no change in agar color
Hemolysis
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• Streptococcus pyogenes
• Streptococcus agalactiae
• Streptococcus pneumoniae
• Streptococcus bovis
• Viridians Streptococcus
• Enterococcus faecalis
• Enterococcus faecium
Streptococcus 10
• Lancefield groupings
• Brown’s classification
• Media
• Microscopic
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• Gram Stain• GPC in chains
• Colony Morphology• Small, white, transparent, smooth colony with well-defined zone beta-hemolysis
• Biochemical Tests• Catalase• Strep Grouping
• Pathology• Infections• Post-streptococcal sequelae
• Virulence Factors
Streptococcus pyogenes
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• Gram Stain• GPC in chains
• Colony Morphology• Small, greyish-white, transparent, smooth colony with small zone beta- hemolysis
• Biochemical Tests• Catalase• Strep Grouping • Hippurate• CAMP
• Pathology• Neonatal sepsis• Neonatal meningitis
Streptococcus agalactiae
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• Gram Stain• GPC in pairs (lancet- shaped)
• Colony Morphology• Small, round, glistening, mucoid, dome -shaped colony with alpha - hemolysis
• Biochemical Tests• Catalase• Optochin (P) • Bile solubility
• Pathology• Pneumonia, sinusitis, otitis media, bacteremia, meningitis
Streptococcus pneumoniae
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• Gram Stain
• GPC in chains
• Colony Morphology
• Small, round, colony with alpha -hemolysis
• Biochemical Tests
• Catalase
• Optochin (P)
• Pathology
• Normal flora, opportunistic, subacute bacterial endocarditis
Viridians Streptococcus
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• Gram Stain• GPC in chains
• Colony Morphology• Small, greyish, smooth colony with gamma-hemolysis
• Biochemical Tests• Catalase• PYR• Bile Esculin• NaCl
• Pathology• Opportunistic
Streptococcus bovis
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• Gram Stain• GPC in chains
• Colony Morphology• Small, greyish, smooth colony with gamma-hemolysis
• Biochemical Tests• Catalase• PYR• Bile Esculin• NaCl
• Pathology• UTIs, Wounds, endocarditis, etc
Enterococcus spp.
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• Streptococus• Penicillin is drug of choice
• Group B – typically resistant to tetracyclines
• Vancomycin and linezolid resistance has not been observed
• E. faecalis• Usually susceptible to ampicillin and penicillin.
• Can acquire resistance to vancomycin.
• Occasionally produce beta- lactamase.
• E. faecium• Often resistant to ampicillin and penicillin.
• Can acquire resistance to vancomycin.
• E. gallinarum and E. casseliflavus• Have intrinsic low level vancomycin resistance
Streptococcus -Antibiotic Susceptibility 17
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• A beta hemolytic streptococcus was recovered from a throat swab. Based on the following tests, what is the identification of this organism?
• Bacitracin susceptible and SXT resistant
• A. Group A
• B. Group B
• C. Other Beta-hemolytic Streptococcus
• D. Abiotrophia
• E. Granulicatella
Question
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• Gram Stain• Pleomorphic Gram positive rods • Often palisading • Can be club-shaped
• Colony Morphology• White, non-hemolytic, opaque colonies
• Biochemical Tests• Catalase
• Pathology• Considered normal skin flora or contaminant
Corynebacterium spp. aka Diphtheroids
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• Gram Stain• Pleomorphic Gram positive rods • Often palisading • Can be club-shaped
• Colony Morphology• White, non-hemolytic, opaque colonies
• Biochemical Tests• Catalase• Nitrate positive• Glucose positive• Maltose positive • Sucrose negative • Urease variable
• Virulence Factor
Corynebacterium diphtheriae
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• Gram Stain• Small Gram positive rods (can be coccobacilli)
• Colony Morphology• Grayish white colony, small zone beta-hemolysis
• Biochemical tests• Catalase• Esculin hydrolysis• Hippurate hydrolysis• Motility• Wet prep =• 25°C semisolid media =
• Pathology• Pregnant women: premature labor, spontaneous abortion• Neonates: sepsis, meningitis• Immunocompromised
Listeria monocytogenes
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• Gram Stain• Large gram positive rods• Can see spores (if organism is stressed)
• Colony Morphology• “Ground glass appearance,” Large colonies, rough edges, beta- hemolytic
• Biochemical tests• Catalase• Motility
• Pathology• Considered a contaminant, endophthalmitis, food poisoning (B. cereus)
Bacillus species
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• Gram Stain• Large gram positive rods• Can see spores (if organism is stressed)
• Colony Morphology• “Ground glass appearance,” Large colonies, rough edges, NON- hemolytic
• Biochemical tests• Catalase positive• Non- motile
• Pathology• Causes anthrax
Bacillus anthracis
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• Gram Stain• Gram positive rods in chains
• Colony Morphology• Alpha hemolytic colonies
• Biochemical tests• Catalase negative
• Pathology• Normal female urogenital flora
Other Gram Positive Rods
• Gram Stain• Gram negative rod
• Direct smear: Clue cells
• Colony Morphology• Tiny transparent colonies
• Biochemical tests• Catalase negative
• Pathology• Bacterial vaginitis
• Lactobacillus sp. • Gardnerella vaginalis
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• Utilization of Glucose
• Ferment “F”, oxidize “O” or inactive
• Oxidase
• Positive or negative
• Ability to grow on MacConkey agar
• Some GNRs that grow on BAP are unable to grow on MacConkey agar
Differentiation of Major GNR Genera
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• All ferment glucose• All reduce nitrate to nitrites• All grow on MAC• All are oxidase negative
• Except Plesiomonas
• Majority motile• Gram-negative coccobacilli or rods
• Not very useful in identification other than ruling out other organisms
• Facultatively anaerobic• Culture morphology
• Large moist, gray colonies• Some mucoid
Family: EnterobacteriaceaeGeneral Characteristics
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• Colony Morphology• Most beta-hemolytic
• Biochemical tests• Oxidase• Indole• Motility
• Pathology• Normal colon flora• Cause UTIs, septicemia, neonatal septicemia and meningitis and several GI tract diseases
• Traveller’s diarrhea (ETEC)• Dysentary (EIEC)• Diarrhea and Vomiting (EPEC)• Hemolytic colitis (EHEC)
Lactose-FermentersEscherichia coli
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• Biochemical tests• Oxidase• Indole
• K. pneumoniae =• K. oxytoca =
• Urea• Citrate• Motility
• Polysaccharide capsule• Pathology
• UTIs, pneumonia
Lactose-FermentersKlebsiella
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• Biochemical tests
• Oxidase
• Indole
• Urea
• Citrate
• Motility
Lactose-FermentersEnterobacter
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• Biochemical tests• Oxidase• Indole• H2S
• Motility• Pathology
• Opportunistic
Slow-Lactose FermentersCitrobacter
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• Colony Morphology• Colonies have a salmon red pigment
• Biochemical tests• Oxidase• Indole
• Motility• Pathology
• Opportunistic
Slow-Lactose FermentersSerratia
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Proteus species• Colony Morphology
• Swarming motility
• Biochemical tests• Oxidase• Indole
• Proteus vulgaris =• Proteus mirabilus =
• H2S
• Motility• Pathology
• Cause UTI’s• Opportunistic
ProteeaePhenylalanine deaminase & Urea positive
ProteeaePhenylalanine deaminase & Urea positive
Providencia• Biochemical tests
– Oxidase– Indole– Citrate
• Motility
Morganella• Biochemical tests
– Oxidase– Indole– Citrate
• Motility
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• Biochemical tests
• Oxidase
• Indole
• H2S
• Motility
• Pathology
• Diarrhea
• Septicemia
Obligate PathogensSalmonella
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• Biochemical tests
• Oxidase
• Motility
• Pathology
• Diarrhea
Obligate PathogensShigella
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• Coccibacilli; bipolar staining
• Biochemical tests
• Oxidase negative
• Indole negative
• Motile
• Pathology
• Plague (Y. pestis)
• Diarrhea (Y. enterolitica)
Obligate PathogensYersinia
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• Ferment Glucose
• Ferment Lactose
• Motile @ body temp
• Citrate
• H2S Producers
• Deaminate phenylalanine
• KIA: K/A no H2S
• KIA: A/A no H2S
• KIA: K/K no H2S
• KIA: K/A H2S
• KIA: A/A H2S
Enterobacteriaceae
• P. vulgaris vs. P. mirabilis
• Morganella vs. Providencia
• Enterobacter vs. Klebsiella
• K. pneumoniae vs. K. oxytoca
• E. coli vs. K. oxytoca
• E. aerogenes vs. E. cloacae
• Salmonella vs. Shigella
• Non-fermenting E.coli vs. Edwardsiella
• Providencia vs. Proteus
• Edwardsiella vs. Salmonella
37
• Groupings • Differentiation
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• Gram Stain• Gram negative rod
• Colony Morphology• Beta-hemolytic; flat, spreading colony with fruity, grape-like smell• Growth at 42oC
• Biochemical tests• Glucose• Oxidase
• Pathology• Pneumonia and wounds
Pseudomonas aeruginosa
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• Gram Stain• Gram Negative Rod
• Non-motile• Biochemical tests
• Catalase• Oxidase• Nitrate
• Acinetobacter baumannii• Glucose• Grows at 42°C
• Acinetobacter lwoffii• Glucose • No growth at 42°C
Acinetobacter species
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• Gram negative rod
• Oxidase negative
• Glucose “O”
• No growth at 42°C; Sometimes can develop a lavender-green to light purple pigment
Stenotrophomonas maltophila
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• Three major groups:• V. cholerae O1• V. cholerae O129• V. cholerae non-O1
• Virulence factors• Cholera toxin—Causes mucosal cell hypersecretion of water• Others—Enterotoxins (zonula occludens toxin [ZOT] and accessory cholera enterotoxin [ACE]); O1 and O139
antigens • Spectrum of disease
• Cholera• Profuse, watery diarrhea leading to dehydration (“rice-water” stool)• Hypotension
• Nonepidemic diarrhea, associated with non-O1 group• Vibrio Identification
• Oxidase• 6.5% NaCl• Vibrostatic compound O/129• String test• Sucrose
Vibrio cholerae
41
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• Gram negative rods
• Beta-hemolytic on BAP
• Grows on MAC
• Oxidase positive
• Glucose “F”
Aeromonas hydrophilia
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• Curved Gram negative rod
• Grows at both 37°C & 42°C in 10% CO2 (microaerophilic)
• Oxidase positive
• Darting motility on wet prep
• Hippurate hydrolysis positive
Campylobacter jejuni
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• Curved Gram negative rod
• Urease positive
• Oxidase positive
Helicobacter pylori
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• Gram negative coccobacilli• Fastidious (agar, factors, CO2)• Porphyrin test• Pathology
• H. influenzae: Meningitis, epiglottitis, pneumonia, otitis media• H. aegyptius: conjunctivitis• H. ducreyi: STD - chancoid
Haemophilus species
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• Gram Stain
• Gram-negative rods
• Colony Morphology
• Nonhemolytic colonies
• Pathology
• Colonize the URT
Other Gram-negative Rods Eikenella corrodens
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• Gram-negative bacilli• Require an increased CO2 (5%-10%) environment• Significant cause of endocarditis• Usual flora of the oral cavity• Thus are pathogens associated with human bite wounds causing septicemia and subacute
endocarditis• Opportunists in immunocompromised hosts
• H – Haemophilus spp. (Now Aggregatibacter aphrophilus)• A – Actinobacillus actinomycetemcomitans (Now Aggregatibacter actinomycetemcomitans)• C – Cardiobacterium hominis• E – Eikenella corrodens• K – Kingella spp.
HACEK GroupGeneral Characteristics
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• Gram Stain
• Gram-negative coccibacilli
• Zoonotic infection acquired from animals or animal products
• Most common species for human brucellosis
• B. mellitensis (most common isolate), B. abortus, B. canis, B. suis
• Pathology
• Brucellosis or undulant fever
Brucella species
CO2 Urease H2S Inhibition Thionine
Inhibition
Fuchsin
B.abortus +/- 2 hrs + + (S) - (R)
B.melitensis - V - - (R) - (R)
B.suis - 15 min +/- - (R) + (S)
B.canis _ 15 min - - (R) + (S)
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• Gram Stain
• Gram-negative coccibacilli
• Facultative intracellular parasite
• Strict aerobe
• Pathology
• Zoonotic infection
• Causes tularemia
• Acute febrile, granulomatous disease with rapid onset and flulike symptoms
Francisella species
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• Intracellular parasite of cells• Enter and multiply within host cells• Particularly bronchoalveolar macrophages• Legionella pneumophila
• Legionnaires’ disease• Pontiac fever
• Sources• Present in environmental water sources• Air conditioning systems
• Detection• Culture: BCYE agar• Antigen in the urine: Sensitive• Direct fluorescent antibody staining• Serology
Legionella Species
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• Major pathogens• Bordetella pertussis• Bordetella parapertussis• Bordetella bronchiseptica
• Highly contagious disease• Exposure and incubation period of 1-2 weeks• Initially cold or flulike symptoms, sneezing, runny nose• Catarrhal phase 1-2 weeks (highly contagious)
• Paroxysmal phase: Sudden severe repetitious coughing• Convalescent phase
• Begin recovery about 4 weeks after initial symptoms• Decrease in bouts of coughing but may take weeks or months for complete resolution
• Pathology• Causes ____________________• B. bronchiseptica - Opportunistic pathogen involved in pneumonia and wound infections
Bordetella Species
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• Gram Stain• Gram negative diplococci• Kidney bean shaped
• Colony Morphology• On modified Thayer- Martin (MTM) agar:• Small, gray, translucent, raised
• Biochemical tests• Catalase• Oxidase• Carbohydrate utilization ->
• Pathology• N. gonorrhea: Cervicitis, urethritis, conjunctivitis• N. meningitidis: meningococcemia
• Antimicrobials• Penicillin is drug of choice• Resistance observed- Perform beta-lactamase
Pathogenic Neisseria
Organism Glucose Maltose Lactose Sucrose
Neisseria gonorrhoeae
Neisseria meningitidis
Neisseria lactamica Positive Positive Positive Negative
Nonpathogenic Neisseria Positive Positive Negative Positive
Moraxella catarrhalis
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• Anaerobic organism• Gram Stain
• Large gram positive rods• Blunt, rounded ends (“boxcar” shaped)• Can see spores (if organism is stressed)
• Colony Morphology
• Biochemical tests• Catalase
• Pathology• Gas gangrene, food poisoning
Clostridium perfringens
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• Clostridium difficile
• Clostridium tetani
• Clostridium botulium
Other Clostridium
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• Main group of anaerobes isolated
• Consists 13 species
• Most common – B. fragilis, B. thetaiotamicron
• Natural habitat
• Predominant NF colon
• Also found oropharynx, female genital tract
• Clinical significance
• Mainly infections below diaphragm (intraabdominal, liver abscesses, other)
• GS- pale-staining neg rod, rounded ends, vacuoles, pleomorphic
• Colonies- white-gray, translucent or semi-opaque, NH
B. fragilis group5
5
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Acid –Fast Stains• Ziehl-Neelson
• Kinyoun
Media• Lowenstein-Jensen
• Middlebrook Medium
• Mycobacterium culture bottles
Specimens• Respiratory
• Urine
• Blood & bone marrow
• Tissue & body fluids
Lipid-Mycolic Acid WallsMycobacterium
• M. tuberculosis
• M. bovis
• M. ulcerans
• M. avium
• M. kansasii
• M. xenopi
• M. lepreae
56
Pathogens
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• Highly fastidious
• Very small cell size (0.3 x 0.8 μm)
• No cell wall
• Two mycoplasma species are known human pathogens• Mycoplasma pneumoniae• Mycoplasma hominis
• Ureaplasma urealyticum
Cell-Wall Deficient Bacteria
57
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Any Questions? 58
SCHOOL OF HEALTH PROFESSIONS
• www.TeraWebb.comWebsite
• www.linkedin.com/in/terawebb LinkedIn
• @TERAologyTwitter
• Tera_webbInstagram
• teralw@uab.eduEmail
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• Growth Rate• Rapid, intermediate, slow growers
• Incubation conditions
• Colony Morphology• Hyaline or dematiaceous• Pigment, texture, topography, etc
• Microscopic Morphology (natural growth state)• Hyphae • Type of Sporulation
• Mold to yeast conversion
• Cycloheximide resistance
Criteria for ID of Molds 59
Superficial Mycosis
• Malassezia furfur– Patchy lesions or scaling of varying pigmentation
• Usually on chest, trunk, abdomen
– May be cause of dandruff– Skin scrapings in KOH prep
• Yellow fluorescence with Wood’s lamp
– Spaghetti and meatballs microscopic morphology
• Piedraia hortae– Black piedra
• Hairs of scalp - Black gritty nodules
– Tropical Africa, Asia, and Latin America
• Trichosporum– White piedra on hair shaft– Opportunistic pathogen
• Endemic in tropical South America, Far East, and Pacific– Grow rapidly on primary media
• Smooth colonies cream colored and yeastlike– Some wrinkling upon maturation
• Utilization of potassium nitrate, urease positive
• Hortaea (Phaeoannellomyces) werneckii– Tinea nigra
• Brown to black nonscaly macule - Palms of hands and soles of feet• No inflammation or reaction to fungus
– Skin scraping in 10%-20% KOH• Septate hyphae and budding cells
– Culture• Shiny, moist, yeastlike colonies brown to olive or greenish black
Cutaneous Mycosis
• Epidermophyton floccosum– Colony morphology
• Yellow to yellow tan
– Microscopically• Macroconidia & macroconidia
– 3-5 cells with thin smooth walls– Look like beaver tails
• Microsporum canis– Colony
• Initially white and silky • Reverse developing a lemon yellow pigment on reverse
– Microscopically• Spindle-shaped, multicelled macroconidia and scattered
microconidia• Pointed and slightly turned at one tip• Thick spiny (echinulate) wall
• Microsporum gypseum– Colony morphology
• Flat initially white turning light brown to reddish-brown on maturity
• Sugary or granular appearance
– Microscopically• Macroconidia
– Abundant with long and rounded tips
• Echinulate wall with less thick septations• Clublike macroconidia
• Microsporum audouinii– Slow-growing anthropomorphic dermatophyte
• Used to be leading cause of tinea capitis
– Rare conidia• Some isolates produce terminal chlamydoconidium-like
swellings
– Colonies• Cottony and white with little to no pigment on reverse
Cutaneous Mycosis
• Trichophyton mentagrophytes– Macroscopically
• Downy to granular based on number of microconidiapresent
– Microscopically• Microconidia form loose grapelike clusters (en grappe)
– Globose to tear shaped• Macroconidia present in very low numbers or absent
– Thin smooth cigar-shaped four to five cells separated by parallel cross-walls
• Trichophyton rubrum• Colony morphology
– Initially white with cottony, velvety, or granular colonies– Key observation
• Water soluble wine-red pigment on the reverse of the colony
• Microscopically– Microconidia are tiny clavate or peg shaped and
distributed on either side of the hyphal strands• “Birds on a fence”
– Macroconidia similar to T. mentagrophytes• Elongated and pencil shaped• Rare
• Trichophyton tonsurans– Colony morphology
• Granular buff surface with deep radial rugae on maturation
– Microscopically• Microconidia vary in size
– Elongated – Club shaped– Balloon shaped forms with small tear-shaped microconidia
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• Involve deeper skin layers• Generally dissemination through the blood does not occur
• Clinical features• Chromoblastomycosis - Dematiaceous molds
• Chronic infection: Nonhealing ulcers• Eumycotic mycetoma - P. boydii (Scedosporium boydii)
• Draining sinus tracts
• Lymphocutaneous infection that may become systemic• Sporothrix schenckii
• Mold• Yeast: cigar-shaped
Subcutaneous Mycoses
Systemic Mycosis
Coccidioides immitis
• Coccidioidomycosis• Endemic to Southwestern United States
– Soil
• Colony morphology– Cobweb-like, with gray-white mycelium– Highly infectious
• Microscopically– Mold form
• Hyphae are delicate and break up into barrel-shaped arthroconidia that are separated by empty spaces when stained (every other one)
– Spherule form (do not form yeast)• Observed in tissue sections
Histoplasma capsulatum
• Commonly found in the North American river basins– St. Lawrence, Ohio, Mississippi, Missouri, river valleys – Soil rich in organic content (bird and bat excreta)
• Colony morphology– Mold
• Mycelium initially white but turning gray or gray-brown– Yeast
• Typically smooth, yellow-white, and glistening with pasty consistency
• Microscopically– Yeast
• Single bud connected by a delicate filament• In tissue, yeast cells are clustered in macrophages
surrounded by clear space (looks pseudoencapsulated)
Blastomyces dermatitidis
• Soil mold– Found in KY, MS, AR, NC, TN, LA, IL, WI
• Colony morphology– Gray-white or light buff colored with delicate, silky,
hairlike, mycelium
• Microscopically - mold– Delicate hyphae 1-2 μm in diameter hyline, and
septate– Oval or pyriform conidia Form “lollipop-like” structure
• Yeast (35° C) on enriched agar– Colony morphology
• Small, slightly convex, smooth off yellow or buff pigmentation
– Microscopically• Single bud attached by a broad base• Can be confused with C. immitis
Penicillium marneffei
• Infections in immunocompromised patients• Resembles H. capsulatum
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• Zygomycota• Multinucleate molds, most are saprobes• Nonseptate fungi• Mucor, Absidia, Rhizopus, Rhizomucor
• Aspergillus• Several species
• A. fumigatus• A. flavus• A. terreus• A. niger
• Penicillium
Opportunistic Mycosis 66
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• Candida albicans• Thrush leading to systemic infections• Yeast infections
• Candida glabrata• Aggressive infections and difficult to treat
• Cryptococcus neoformans• Opportunistic infection
• Meningitis, pneumonia, and septicemia• Characteristics
• Mucoid appearance due to capsule• India ink test
• Black background with clear halos around organism• Being replaced by latex agglutination
• Blastoconidia only
Agents of Yeast Infections
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• P. jiroveci• Most infections occur by 2-4 years old
• Asymptomatic in healthy immunocompetent individuals
• Symptoms• Fever, nonproductive cough, and difficulty breathing
• Chest radiographs may show interstitial infiltrates
• Life cycle• Nonfilamentous fungus• Three stages
• Trophozoite• Multiply by binary fission
• Precyst
• Cyst• Infective stage
• Diagnosis• Biopsy and aspirates of the lung• Calcofluor white
• Blue-white color when stained and viewed under UV light
Pneumocystis
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• Adenoviridae
• Mostly respiratory illness
• May cause gastroenteritis, conjunctivitis, cystitis, rashes
• Hepadnaviridae
• Hepatitis B
• Herpesviridae• Herpes simplex 1 and 2• Varicella-zoster
• Papillomaviridae• Warts• Possibly cervical carcinomas
DNA Viruses
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• Parvoviridae• Only one causes human disease: B19
• Others cause disease in animals
• Poxviridae• Largest viruses• Causative agent of smallpox
DNA Viruses 70
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• Orthomyxoviridae
• Include influenza A, B, and C viruses
• Type A—most virulent in humans
• Coronaviridae
• Respiratory and enteric disease
• Picornaviridae
• Important pathogens, include Enterovirus, Rhinovirus, Hepatovirus, Aphthovirus, Parechovirus, Erbovirus, Kobuvirus, Teschovirus
• Large family, smallest RNA viruses
• Hepeviridae
• Paramyxoviridae
• Filoviridae & Bunyaviridae
• Hemorrhagic Fevers
RNA Viruses 71
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• Rhabdoviridae• Infect plants, insects, fish, birds, mammals, including humans
• Rabies virus belongs to this group
• Reoviridae• Rotavirus: gastroenteritis—common in children— accounts for approximately 50% of all cases of
diarrhea in children requiring hospitalization
• Retroviridae• Oncovirinae, Lentivirinae, Spumavirinae• Example: HIV
• Togaviridae• Alphaviruses, Rubivirus—rubella virus
• Flaviviruses• Yellow fever, West Nile virus
RNA Viruses 72
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• Defined by three common characteristics
• They are eukaryotes
• They are single-celled
• They lack a cell wall
• Majority are motile due to cilia, flagella, and/or pseudopodia
• Two distinctive forms
• Trophozoites
• Cysts
Protozoans 73
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• Amebas
Move by pseudopods
• Entamoeba histolytica
• Entamoeba coli
• Acanthamoeba
• Naegleria fowleri
Protozoan Parasites
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• Flagellates
• Simple
• Giardia
• Trichomonas
• Several life-cycle forms
• Typanosmona cruzi
• Typanosoma brucei
• Leishmania
Protozoan Parasites
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• Ciliates
• Balantidium coli
• Apicomplexa
Intracellular
• Plasmodium
• Toxoplasma
• Pneumocystis
• Cryptosporidium
Protozoan Parasites
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• Often found in blood, feces, and urine
• Must be distinguished from microbes
• Many parasitic helminths spend much of their life cycle in mammalian host
• Most of the ones affecting humans belong to flatworms and roundworms
• Adult animals usually large enough to be seen with the naked eye
• Eggs and larvae—microscopic
Helminths 77
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• Trematodes a.k.a. flukes
• Schistosoma
• Cestodes a.k.a. tapeworms
• Taenia saginata
• Taenia solium
• Hymenolepis nana
Helminth Parasites
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• Nematodes a.k.a. roundworms
• Necator
• Ascaris
• Enterobius
• Loa Loa
• Filiariasis
• Wuchereria
• Brugia
Helminth Parasites
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